Construction Cost Estimating


Detailed processes for designing Pile Cap

A pile cap stands for a dense concrete mat that is supported with concrete or timber piles and directed to soft or unsteady ground to develop a proper stable foundation. It generally creates part of the foundation of a building, normally a multi-story building, structure or support base for heavy equipment. The cast concrete pile cap will disperse the load of the building into the piles. The same type of structure to a pile cap is called a raft. It is a concrete foundation floor that is supported directly onto soft soil to be ready for subsidence.

With reference to IS 2911 (Part I/ Sec 3) -2010, the pile is designed by accepting that the load from column is distributed at 45° from the top of the cap up to the mid depth of the pile cap from the base of the column or pedestal. The reaction from piles is also considered to be circulated at 45° from the edge of the pile, up to the mid depth of the pile cap. Based on this, the highest bending moment and shear forces should be measured at crucial sections.

Concerned assumptions
(i) Pile cap is accurately inflexible.

(ii)No bending moment is transferred to piles from pile caps as pile heads are hinged to the pile cap
(iii) As the piles are short and elastic columns, the deformations and stress distribution are planer.

(i) Shape of pile cap.
(ii) Depth of pile cap.
(iii) Required Amount of steel.
(iv) Positioning of reinforcement.

Download Design of Pile Cap Worksheet

Design Method:
Ascertain number of pile, Placement of pile cap and plane dimension, Pile cap initial depth, Examine forces in piles

Detailed processes for designing Pile Cap

Examine punching shear, Examine shear, Design of moment, Examine bond, details for reinforcement